Data Sheet 26300.2A† 8932-A VOICE-COIL MOTOR DRIVER RET REF 1 V FLT 2 PROTECT 28 RET SET 27 V SENS 26 V LOAD – CIRCUIT V BEMF 3 GROUND 4 25 V SENS FB UV SET 5 24 SGND N R OUT P 6 23 OUTP OUT 7 VDD 22 SWITCH 8 + – IN N 9 OUT SW 10 RETRACT 11 FAULT 12 MP RESET 13 SIGNAL SUPPLY 14 21 OUT N 20 SGND P 19 ACT FB 18 PWR OFF 17 H GAIN + 16 REFERENCE – 15 ACT + V REF – + 2V PROTECT CIRCUIT V CC LOAD SUPPLY Dwg. PP-042B ABSOLUTE MAXIMUM RATINGS Supply Voltages, VCC and VDD ............ 6.0 V Output Current, IOUT (peak) ........... ±600 mA (continuous) ........................... ±500 mA Analog Input Voltage Range, VIN .................................... -0.3 V to VCC Logic Input Voltage Range, VIN ............................... -0.3 V to +6.0 V Package Power Dissipation, PD ......................................... See Graph Operating Temperature Range, TA ..................................... 0°C to +70°C Junction Temperature, TJ ............... +150°C† Storage Temperature Range, TS ................................ -55°C to +150°C Providing control and drive of the voice-coil motor used for head positioning in 5 V disk drive applications, the second-generation A8932CLWA is a full-bridge driver that can be configured so that its output current is a direct function of an externally applied control voltage or current. This linear current control function is supplemented by additional circuitry to protect the heads and the data disk during system failure or normal system shutdown. The two ±500 mA MOS driver outputs provide very low saturation voltage and minimal power dissipation. Additional headroom is achieved by the sense-FET structure eliminating the need for an external current-sense resistor. Internal circuitry can be configured to provide closed-loop velocity control of the actuator by utilizing the generated back-EMF of the voice-coil motor. Thermal protection and under-voltage lockout disables the system in a controlled sequence if a fault condition occurs. FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Class-B, 2 Ω rDS(on) at 500 mA Output Lossless Current Sensing Zero Current-Loop Deadband High Transconductance Bandwidth User-Adjustable Transconductance Gain Digital Transconductance Gain Switch (4:1 Ratio) 5 Volt Monitor with Selectable UV Trip Point Retract Circuitry Functional to 0 Volts Sleep Mode Function Internal Back-EMF Velocity Loop Option Internal Thermal Shutdown Circuitry † Fault conditions that produce excessive junction temperature will activate device thermal shutdown circuitry. These conditions can be tolerated, but should be avoided. Output current rating may be restricted to a value determined by system concerns and factors. These include: system duty cycle and timing, ambient temperature, and use of any heatsinking and/or forced cooling. For reliable operation the specified maximum junction temperature should not be exceeded. Always order by complete part number, e.g., A8932CLWA . 8932-A VOICE-COIL MOTOR DRIVER FUNCTIONAL BLOCK DIAGRAM SIGNAL SUPPLY LOAD SUPPLY 14 VDD V CC ACT FB 19 VOLTAGE-SENSE AMP 22 – I SENSE + 26 V LOAD 20 SGND P + 23 OUT P – 21 OUT N 24 SGND N 25 V SENS FB 27 V SENS + ERROR – AMP ACT 15 POWER AMP + REFERENCE 16 2V H GAIN 17 POWER CONTROL LOGIC PWR OFF 18 REF. CURRENT-SENSE AMP I SENSE – – + REF. TSD FAULT 12 11 + REF. 6 R OUT P RET SET 1 RETRACT 28 RET REF 2 VFLT 3 – RETRACT CONTROL 4 8 GROUND SWITCH 2.0 1.5 /W R, C AI 66° EE = FR JA R θ ALLOWABLE PACKAGE POWER DISSIPATION IN WATTS UVSET 5 VBEMF MP RESET 13 PROTECTION CIRCUITRY 1.0 0.5 0 25 50 75 100 125 AMBIENT TEMPERATURE IN °C 150 Dwg. GP-034 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 Copyright © 1992, 1995 Allegro MicroSystems, Inc. 9 IN N 7 OUT 10 OUT SW Dwg. FP-024D 8932-A VOICE-COIL MOTOR DRIVER ELECTRICAL CHARACTERISTICS at TA = +25°C, VCC = VDD = 5.0 V, VREF = VIN = 2.0 V, Load = 150 µH/3.5 Ω (unless otherwise noted). Limits Characteristic Symbol Test Conditions Min. Typ. Max. Units — — ±50 mV Error Amplifier Input Offset Voltage VIO ILOAD = 0 mA Current Gain AiH H GAIN ≥ 3.5 V 7200 8000 8800 — AiL H GAIN ≤ 0.7 V 1800 2000 2200 — IOUT = 5 mA to 500 mA, Ai = AiL — — ±10 % IOUT = 5 mA to 500 mA, Ai = AiH — — ±10 % VREF 1.5 — 2.5 V Voltage Gain AVD 0.36 0.40 0.44 — Output Offset Voltage VOO ILOAD = 0 mA — — ±25 mV Amplifier Error EVD (Rs x ILOAD / (Ai x VSENSE)) - 1 — 1.0 — — Input Offset Voltage ViO ILOAD = 0 mA, Ai = AiL — — ±25 mV ILOAD = 100 mA — 2.0 2.5 Ω ILOAD = 500 mA — 2.0 2.5 Ω VOUT(P) - VOUT(N) - VRETSET — — ±100 mV -3 dB 1.0 — — kHz Current Gain Linearity Reference Voltage Range EL(adj) Voltage-Sense Amplifier Current-Sense Amplifier Output Drivers Total On Resistance rDS(on) (Source + Sink) Retract Output Voltage Error Full Power Bandwidth EOUT(PN) BW Uncommitted Op Amp Voltage Gain AVS — 91 — dB Unity Gain Bandwidth BW — 1.0 — MHz CLOAD — 40 — pF Slew Rate SR — 4.2 — V/µs Output Voltage VO VSWITCH ≤ 0.7 V 2.5 — 3.5 V VOSW VSWITCH ≥ 3.5 V 2.5 — 3.5 V Max. Load Capacitance Max. Output Current IO — ±250 — µA Input Offset Voltage VIO — <±10 — mV Continued next page… Negative current is defined as coming out of (sourcing) the specified device terminal. Typical Data is for design information only. www.allegromicro.com 8932-A VOICE-COIL MOTOR DRIVER ELECTRICAL CHARACTERISTICS at TA = +25°C, VCC = VDD = 5.0 V, VREF = VIN = 2.0 V, Load = 150 µH/3.5 Ω (unless otherwise noted). Limits Characteristic Symbol Test Conditions Min. Typ. Max. Units Miscellaneous Supply Voltage Under-Voltage Lockout Voltage Fault Logic Output VCC Operating 4.5 5.0 5.5 V VDD Operating 4.5 5.0 5.5 V VCC VCC = VDD 3.9 4.2 4.35 V VRETRACT ≥ 3.5 V — — 500 mV VRETRACT ≤ 0.7 V 4.5 — — V VFLT = 2.25 V — >20 — µA VRETRACT ≥ 3.5 V 4.5 — — V VRETRACT ≤ 0.7 V, IMPREST = 1.5 mA — — 800 mV Outputs Balanced, No Load — — 10 mA Sleep Mode, PWR OFF = VCC — — 2.0 mA VIN(0) — — 0.7 V VIN(1) 3.5 — — V TJ — 165 — °C ∆TJ — 20 — °C VFAULT IFAULT Power-On Reset VMPRESET Total Supply Current Logic Input Voltage Thermal Shutdown Temperature Thermal Shutdown Hysteresis ICC + IDD Negative current is defined as coming out of (sourcing) the specified device terminal. Typical Data is for design information only. The products described here are manufactured under one or more U.S. patents or U.S. patents pending. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro products are not authorized for use as critical components in life-support devices or systems without express written approval. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 8932-A VOICE-COIL MOTOR DRIVER TERMINAL FUNCTIONS Term. Terminal Name 1 RET REF 2 VFLT 3 VBEMF 4 GROUND 5 UVSET Under-voltage trip point reference input. Set internally to 4.2 V but may be overridden by external resistor divider. (Equation 4). 6 ROUT P Source driver used for retract; externally connected to OUTP. 7 OUT 8 SWITCH 9 INN 10 OUTSW 11 RETRACT 12 FAULT 13 MPRESET 14 SIGNAL SUPPLY 15 ACT 16 REFERENCE 17 H GAIN 18 PWR OFF 19 ACTFB Input connection for feedback network which sets the error amplifier gain and bandwidth. 20 SGNDP Power ground for the OUTP sink driver. 21 OUTN 22 LOAD SUPPLY 23 OUTP 24 SGNDN Power ground for the OUTN sink driver. 25 VSENS FB Input connection for feedback network which sets the current-sense amplifier gain and bandwidth. Also called gm SET. 26 VLOAD An output voltage proportional to the load voltage. Used in conjunction with closed-loop velocity control. 27 VSENS Voltage output representing load current (Equation 2). Also called MONITOR. 28 RET SET www.allegromicro.com Function The reference supply for setting the voltage across the load during retract. Reservoir (energy storage) capacitor used to operate fault circuitry. Back-EMF voltage from spindle motor used to retract heads during loss of power. Circuit reference. Output of uncommitted operational amplifier. Logic input for transmission gate; a high level connects OUT to OUTSW. Inverting input to uncommitted operational amplifier. Transmission-gated output of uncommitted operational amplifier. An active-low logic input that initiates the retract sequence. A logic low at this MOS output indicates a thermal shutdown, under-voltage fault, or retract command. (Power-On Reset) A logic low at this open-collector output may be used to reset the system on under-voltage fault or power on. VCC; low-current supply voltage in the range of 4.5 V to 5.5 V. Input which controls the current in the load. Transconductance gain is set with an external resistor in series with this input (Equation 1). VREF; reference input for all amplifiers; ac ground. Logic input to switch the error amplifier transconductance gain: LOW = 2000, HIGH = 8000. An active-high logic input that puts the device in a “sleep mode”. All fault circuitry remains active. Power output. Sinks current when VACT < VREF. VDD; high-current supply voltage for the voice-coil motor. Power output. Sinks current when VACT > VREF. An external resistor divider to set the retract voltage across the load. Used in conjunction with VRET-REF (Equation 3). 8932-A VOICE-COIL MOTOR DRIVER DEVICE DESCRIPTION Current Amplifier. The A8932CLWA voice-coil motor driver features a wide transcon-ductance bandwidth and minimal crossover distortion. The transconductance gain is user selectable: gm = Ai Rgm (Equation 1) where Ai is either 2000 (H GAIN = Low) or 8000 (H GAIN = High). The back-EMF voltage represents the velocity of the actuator. By subtracting the ILOADRLOAD voltage component from the voltage across the load, the back-EMF term can be isolated and fed back to close a velocity control loop. The amplifier output voltage VLOAD is proportional to the voltage across the load (AVD[VOUTN - VOUTP]). RS is selected so that VSENSE represents ILOAD while R3 is dependent on RLOAD as shown in the following equations: VLOAD = -AVD ([ILOAD RLOAD] + VBEMF) The error amplifier’s bandwidth and load compensation zero are set utilizing external resistor and capacitor feedback components around the amplifier. VSENSE = RS ILOAD/AiL The actuator main loop compensation can be set by applying a square wave and adjusting RZ and CZ for optimum response. where Ai = 2000 (H GAIN = logic Low) OUTSW = 0.4 (VBEMF R1/R2) Current and Voltage Sensing. The load current is sensed internally. Three auxiliary amplifiers are also included to allow various control functions to be implemented. The first of these amplifiers provides a voltage output that is proportional to the load current: VSENSE R I = S LOAD Ai R3 = R2 RVgm VBEMF = 0.4 Rgm R1 VIN (Equation 2) The second and third auxiliary amplifiers may be used in conjunction with the first to provide a closed-loop velocity control system for the actuator arm during a controlled retract for head parking. This is achieved by determining the back-EMF voltage generated by the voice coil and feeding back this information to the main actuator control input. The back-EMF feedback voltage can be switched in as required by means of the SWITCH logic input. BW = 0.4 IN 1/Rgm + ∑ Ai R1 KB KT Ai 2π RVGM R2 J where J is the moment of inertia, KB is the back-EMF motor constant, and KT is the torque constant. Velocity loop compensation = LLOAD/RLOAD = R1 C1 = R3 C2. A i = 2000 or 8000 V R2 RS 0.4 Ai RLOAD KT /J .. Ø . Ø KB 1/S – 1/R Vgm 0.4 R1 /R2 K1 VBEMF Dwg. OP-003B 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 8932-A VOICE-COIL MOTOR DRIVER Power for the retract function is provided by the rectified back EMF of the spindle motor by way of the VBEMF terminal. The A8932CLWA will perform the retract function under low supply conditions (nominally down to 2 V). Operation down to almost 0 V requires an energy-storage capacitor at the VFLT terminal. Retract and Brake. A retract-brake sequence is initiated on receiving a fault indication from the internal thermal shutdown (TSD), or under-voltage lockout (UVLO), or an externally applied logic High at the RETRACT input. If the velocity control scheme is implemented, the head can be retracted under the full control of VIN in conjunction with OUTSW back-EMF voltage if no fault condition exists. If a fault condition were to occur however, the retract velocity would be controlled by applying a constant user-defined voltage across the load: 2 R8 1000 + R7 + R8 VRET-SET = Protective Features. The A8932CLWA has a number of protective features incorporated into the design. Undervoltage lockout provides system protection in the event of reduced primary supply voltages. The under-voltage trip point is internally set at approximately 4.2 V. It can be user-defined with an external resistor voltage divider: (Equation 3) 2 (R5 + R6) R6 where R5 + R6 << 200 kΩ. where R7 + R8 >> 1000 Ω. UVTRIP = When the sequence is operated, the output voltage is forced to approximately VRET-SET to retract the heads, and then a fault command (“brake”) is sent to the spindle motor driver. The user determines the total time for the retract sequence, before the spindle brake is enabled, by the choice of an external resistor and capacitor at the FAULT output. Thermal shutdown circuitry is included to protect the device from excessive junction temperature. It is only intended to protect the chip from catastrophic failures due to excessive junction temperature. TEST CIRCUIT AND TYPICAL APPLICATION +5 V RZ V CC VOLTAGE-SENSE AMP VDD – I SENSE + V CZ Rgm ERROR – AMP IN X + POWER AMP VOICE COIL MOTOR V REF + + V REF = 2 V – 2V H GAIN R FAULT ≥ 200 kΩ I SENSE – V REF TSD PROTECTION CIRCUITRY + R C2 3 R1 – + R Vgm X RETRACT R5 R7 R6 BACK EMF FROM SPINDLE MOTOR RS – C1 RETRACT CONTROL VREF V CC R2 CURRENT-SENSE AMP POWER CONTROL LOGIC PWR OFF R8 VDD SWITCH DIODE FOR RETRACT FUNCTION OTHERWISE SHORT TO SUPPLY Dwg. EP-041D www.allegromicro.com (Equation 4) 8932-A VOICE-COIL MOTOR DRIVER Dimensions in Inches (for reference only) 28 15 0.0125 0.0091 0.419 0.394 0.2992 0.2914 0.050 0.016 0.020 0.013 1 2 0.050 3 0° TO 8° BSC 0.7125 0.6969 0.0926 0.1043 0.0040 MIN. Dwg. MA-008-28A in Dimensions in Millimeters (controlling dimensions) 28 15 0.32 0.23 10.65 10.00 7.60 7.40 1.27 0.40 0.51 0.33 1 2 1.27 3 18.10 17.70 BSC 0° TO 8° 2.65 2.35 0.10 MIN. Dwg. MA-008-28A mm NOTES: 1. Lead spacing tolerance is non-cumulative. 2. Exact body and lead configuration at vendor’s option within limits shown. 3. Supplied in standard sticks/tubes of 27 devices or add “TR” to part number for tape and reel. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000